Low profile self-ligating orthodontic brackets and methods of using such orthodontic brackets

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/743,700, filed Mar. 23, 2006, the disclosure of which is hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The invention relates generally to orthodontic brackets and, more particularly, to self-ligating orthodontic brackets and methods of using self-ligating orthodontic brackets.

BACKGROUND OF THE INVENTION

Orthodontic brackets represent principal components of all corrective orthodontic treatments devoted to improving a patient's occlusion. In conventional orthodontic treatments used for cosmetic enhancement of teeth, brackets are affixed to the patient's teeth and an archwire is engaged into a slot of each bracket. The archwire applies corrective forces that coerce the teeth to move into correct positions. The archwire forms a track to guide movement of the brackets and the associated teeth to desired positions for correct occlusion.

Self-ligating orthodontic brackets have been developed that eliminate the need for ligatures by relying on a movable cover, such as a slide, for captivating the archwire within the bracket's archwire slot. Self-ligating orthodontic brackets provide greater patient comfort, shorter treatment time, reduced chair time in the dental operatory, and more precise control of tooth translation. Traditional ligatures (e.g., elastomeric ligatures or metal wires) are also difficult to apply to each individual bracket, which is simplified by self-ligating types of orthodontic brackets. Elastomeric ligatures, which may be susceptible to decay and deformation, may also contribute to poor oral hygiene. Self-ligation also reduces the risks of soft-tissue injury to the patient's mouth.

Conventional self-ligating orthodontic brackets are relatively large in comparison to orthodontic brackets that are ligated conventionally using a ligature. The size discrepancy arises because of the need to engineer the moving parts of the self-ligation mechanism into the construction of the orthodontic bracket. The size difference also results in a relatively high physical profile for self-ligating orthodontic brackets as these brackets project a greater distance from the tooth surface than conventionally-ligated orthodontic brackets. The result of these deficiencies is that self-ligating orthodontic brackets have a higher physical profile that may result in patient discomfort, higher visibility, and poor patient hygiene.

Accordingly, there is a need for a self-ligating orthodontic bracket characterized by a low physical profile that overcomes these and other deficiencies of conventional self-ligating orthodontic brackets.

SUMMARY OF THE INVENTION

In one embodiment of the invention, an orthodontic bracket comprises a bracket body including a lingual surface configured to be mounted to a tooth, a labial surface, and an archwire slot in the labial surface. The orthodontic bracket further comprises a latching member coupled by a hinge pin with the bracket body for movement about an axis of rotation defined by the hinge pin. The latching member movable about the axis of rotation between an opened position in which the archwire is insertable into the archwire slot and a closed position in which the latching member retains the archwire in the archwire slot. When the latching member is in the closed position, the latching member is further movable relative to the bracket body in a non-collinear direction relative to the axis of rotation. The hinge pin is formed from a material having a flexibility sufficient to impart a spring bias to the latching member that opposes movement of the latching member in the non-collinear direction.

In another embodiment of the invention, a method is provided for using an orthodontic bracket having a bracket body and a latching member pivotally coupled with the bracket body for movement relative to the bracket body about an axis of rotation. The latching member is movable about the axis of rotation between an opened position in which the archwire is insertable into the archwire slot and a closed position in which the latching member retains the archwire in the archwire slot. The method comprises applying a force to the latching member generally in a non-collinear direction relative to the axis of rotation to move the latching member in the non-collinear direction against a spring bias directed generally opposite to the non-collinear direction.

The self-ligating mechanism of the orthodontic bracket may permit a decrease in the overall bracket height (i.e., the labial-lingual height). As a result, the orthodontic bracket may exhibit improved mechanics, aesthetics, patient comfort, and patient hygiene. The orthodontic bracket lacks a conventional moving slide but, instead, includes a pivoting latch as a self-ligating mechanism used to confine an archwire in the archwire slot. Because the self-ligating components of the orthodontic bracket are at the labial end of the bracket, the bracket may exhibit a relatively low profile when mounted to a tooth surface. As a specific example, the orthodontic bracket does not include a spring as a discrete component in the construction of the self-ligating mechanism.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the principles of the invention.

<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view of an orthodontic bracket in accordance with an embodiment of the invention in which a latching member of the orthodontic bracket is shown in a closed position.

<figref idref="DRAWINGS">FIG. 2</figref> is a front view in partial cross-section of the orthodontic bracket of <figref idref="DRAWINGS">FIG. 1</figref>.

<figref idref="DRAWINGS">FIG. 3</figref> is a side view of the orthodontic bracket of <figref idref="DRAWINGS">FIGS. 1 and 2</figref>.

<figref idref="DRAWINGS">FIG. 3A</figref> is an enlarged view of an encircled portion of <figref idref="DRAWINGS">FIG. 3</figref>.

<figref idref="DRAWINGS">FIG. 3B</figref> is an enlarged view similar to <figref idref="DRAWINGS">FIG. 3A</figref> of an orthodontic bracket in accordance with an alternative embodiment of the invention.

<figref idref="DRAWINGS">FIG. 4</figref> is a front view of a latching member of the orthodontic bracket of <figref idref="DRAWINGS">FIGS. 1-3</figref>.

<figref idref="DRAWINGS">FIG. 5</figref> is a perspective view similar to <figref idref="DRAWINGS">FIG. 1</figref> in which the ligating member of the orthodontic bracket is shown pivoted to an opened position.

<figref idref="DRAWINGS">FIG. 6</figref> is a side view of the orthodontic bracket of <figref idref="DRAWINGS">FIG. 5</figref>.

<figref idref="DRAWINGS">FIG. 7</figref> is a side view of the orthodontic bracket similar to <figref idref="DRAWINGS">FIG. 6</figref> with the latching member pivoted to an intermediate position between the opened and closed positions.

<figref idref="DRAWINGS">FIG. 8</figref> is a cross-sectional view taken generally along line <b>8</b>-<b>8</b> in <figref idref="DRAWINGS">FIG. 7</figref>.

<figref idref="DRAWINGS">FIGS. 9A-C</figref> are a series of side views of the orthodontic bracket of <figref idref="DRAWINGS">FIGS. 1-8</figref> illustrating the process for opening the latching member.

<figref idref="DRAWINGS">FIG. 10</figref> is a perspective view of an alternative embodiment of the invention.

<figref idref="DRAWINGS">FIG. 10A</figref> is an enlarged view of a portion of <figref idref="DRAWINGS">FIG. 10</figref>.

<figref idref="DRAWINGS">FIG. 11</figref> is a cross-sectional view taken generally along line <b>11</b>-<b>11</b> in <figref idref="DRAWINGS">FIG. 10</figref>.

<figref idref="DRAWINGS">FIG. 12</figref> is a perspective view of an alternative embodiment of the invention.

<figref idref="DRAWINGS">FIG. 13</figref> is a cross-sectional view taken generally along line <b>13</b>-<b>13</b> in <figref idref="DRAWINGS">FIG. 12</figref>.

DETAILED DESCRIPTION

With reference to <figref idref="DRAWINGS">FIGS. 1-5</figref>, an orthodontic bracket, generally indicated by reference numeral <b>10</b>, for use in corrective orthodontic treatments generally includes a bracket body <b>12</b>, a latching member <b>14</b>, and a hinge pin <b>16</b> that couples the latching member <b>14</b> with the bracket body <b>12</b>. The latching member <b>14</b> is hinged to the bracket body <b>12</b> by the hinge pin <b>16</b>, which defines a shaft that allows the latching member <b>14</b> to swivel or pivot for moving the latching member <b>14</b> between an opened position (<figref idref="DRAWINGS">FIGS. 5</figref>, <b>6</b>) and a closed position (<figref idref="DRAWINGS">FIG. 1</figref>). The angular range of pivoting movement of latching member <b>14</b> relative to the bracket body <b>12</b> may be less than 180° when the latching member <b>14</b> moves between the opened and closed positions. Portions of the hinge pin <b>16</b> also flex relative to the bracket body <b>12</b>, as described below, to permit the latching member <b>14</b> to be locked with the bracket body <b>12</b> as the latching member <b>14</b> approaches the closed position and to be unlocked to release the latching member <b>14</b> from the closed position for pivoting movement to the opened position.

If orthodontic bracket <b>10</b> is mounted to a tooth in the maxilla, the latching member <b>14</b> may open in the occlusal direction. If orthodontic bracket <b>10</b> is mounted to a tooth in the mandible, the latching member <b>14</b> may open in the gingival direction. However, the invention is not so limited as the latching member <b>14</b> for different brackets <b>10</b> applied to either arch may open in any combination of directions.

The bracket body <b>12</b> and latching member <b>14</b> are constructed using known fabrication methods from conventional materials, including but not limited to a metal like titanium or a ceramic. The bracket body <b>12</b> and latching member <b>14</b> may be constructed of different materials or any combination of conventional materials familiar to a person having ordinary skill in the art. The hinge pin <b>16</b> may be fabricated from any suitable type of flexible material, such as a nickel titanium alloy.

The bracket body <b>12</b> has a bracket base <b>18</b> configured to be adhesive bonded to a buccolabial surface of a tooth (not shown) in any conventional manner such as, for example, with an appropriate orthodontic cement or glue. The bracket base <b>18</b> may have a contoured profile that corresponds to the curved contour of the patient's tooth surface to which the bracket base <b>18</b> is bonded and may carry optional structure (not shown), such as a bond pad, for enhancing the strength of the adhesive bond with the patient's tooth surface.

The bracket body <b>12</b> includes a pair of sidewalls <b>20</b>, <b>22</b> that are substantially parallel to each other and that are oriented generally in gingival-occlusal planes when the bracket base <b>18</b> is secured to the tooth. Bracket body <b>12</b> also includes a pair of sidewalls <b>24</b>, <b>26</b> that are substantially parallel to each other and that are oriented generally in mesial-distal planes when the bracket base <b>18</b> is secured to the tooth. Respective pairs of the sidewalls <b>20</b>, <b>22</b>, <b>24</b>, <b>26</b> converge to define bracket body corners, which may be chamfered or curved.

The bracket body <b>12</b> includes an integral body extension <b>28</b> that projects outwardly beyond sidewall <b>24</b> in either an occlusal or gingival direction when the bracket base <b>18</b> is secured to the tooth. The bracket body <b>12</b> includes another body extension <b>30</b> that projects beyond the opposite sidewall <b>26</b> in the opposite direction to the body extension <b>28</b>. The body extensions <b>28</b>, <b>30</b> may define tie wings providing attachment points to, for example, apply torsional forces to the tooth to which the orthodontic bracket <b>10</b> is attached or if the tooth is severely malpositioned during the initial treatment stages. Body extension <b>28</b>, which is roughly centered between the sidewalls <b>20</b>, <b>22</b> of the bracket body <b>12</b>, includes opposite sidewalls <b>29</b>, <b>31</b>.

An archwire slot <b>32</b> is bounded by two side surfaces <b>34</b>, <b>36</b> and a base surface <b>38</b> that penetrate through the sidewalls <b>20</b>, <b>22</b> to define a channel that extends across the bracket <b>10</b> generally in the mesial-distal direction. The base surface <b>38</b> joins the side surfaces <b>34</b>, <b>36</b> and the distance between the side surfaces <b>34</b>, <b>36</b> determines the physical dimensions of archwires that can be inserted into the archwire slot <b>32</b>. The archwire slot <b>32</b> defines a channel that receives an archwire <b>33</b> for transferring a corrective force from the archwire <b>33</b> to the bracket <b>10</b>, which coerces movement of the tooth to which the bracket <b>10</b> is secured relative to nearby teeth in the patient's mouth. The channel defined by the archwire slot <b>32</b> opens toward either the cheek or lips contingent upon the location within the upper or lower jaw of the tooth to which the bracket <b>10</b> is attached. When the latching member <b>14</b> is in the opened position (<figref idref="DRAWINGS">FIG. 5</figref>), the archwire slot <b>32</b> is accessible for inserting and removing the archwire <b>33</b>. When the latching member <b>14</b> is in the closed position (<figref idref="DRAWINGS">FIG. 1</figref>), the archwire <b>33</b> is secured in the archwire slot <b>32</b> to ligate the archwire <b>33</b> to the bracket <b>10</b>.

The latching member <b>14</b> includes a main body <b>40</b> and arms <b>48</b>, <b>50</b> projecting from one side edge <b>49</b> of the main body <b>40</b>. The arms <b>48</b>, <b>50</b> are separated by a clearance distance adequate to receive the body extension <b>28</b> when the latching member <b>14</b> is mounted to the bracket body <b>12</b>. Recessed regions or lands <b>44</b>, <b>46</b> are disposed adjacent to the opposite sidewalls <b>29</b>, <b>31</b>, respectively, of the body extension <b>30</b>. The lands <b>44</b>, <b>46</b> provide clearance space for the arms <b>48</b>, <b>50</b> and movement of the arms <b>48</b>, <b>50</b> as the latching member <b>14</b> is moved between the opened and closed positions.

With continued reference to <figref idref="DRAWINGS">FIGS. 1-5</figref>, arms <b>48</b>, <b>50</b> are coupled with the hinge pin <b>16</b>. The hinge pin <b>16</b> defines a pivot axis that operates as an axis of rotation <b>41</b> (<figref idref="DRAWINGS">FIG. 2</figref>) about which the latching member <b>14</b> is moved relative to the body extension <b>28</b>. The axis of rotation <b>41</b> coincides with an axis of symmetry for the cylindrical shape of the hinge pin <b>16</b> in the representative embodiment of the bracket <b>10</b>.

A passageway <b>42</b> extends in the mesial-distal direction through the bracket body <b>12</b> and includes opposite open ends that intersect the opposite sidewalls <b>29</b>, <b>31</b> of the body extension <b>28</b>. The hinge pin <b>16</b>, which is longer than the length of the passageway <b>42</b>, is disposed in the passageway <b>42</b>. Opposite ends <b>52</b>, <b>54</b> of the hinge pin <b>16</b> project outwardly from the respective opens ends of passageway <b>42</b>. The passageway <b>42</b> is generally aligned with the axis of rotation <b>41</b>.

Arm <b>48</b> of latching member <b>14</b> includes an opening <b>56</b> that receives one projecting end <b>52</b> of the hinge pin <b>16</b>. Arm <b>50</b> of latching member <b>14</b> includes an opening <b>58</b> that receives the other projecting end <b>54</b> of the hinge pin <b>16</b>. In the representative embodiment, the openings <b>56</b>, <b>58</b> are cylindrical bores penetrating through the respective one of the arms <b>48</b>, <b>50</b>. Each of these engagements, which physically secure the latching member <b>14</b> to the bracket body <b>12</b>, includes sufficient clearance to permit free pivoting motion of the latching member <b>14</b> relative to the bracket body <b>12</b> along the axis of rotation <b>41</b>.

As best shown in <figref idref="DRAWINGS">FIG. 2</figref>, the passageway <b>42</b> has two tubular chambers or regions <b>60</b>, <b>62</b> that collectively extend along the majority of the length of the passageway <b>42</b>. The tubular regions <b>60</b>, <b>62</b> intersect the respective sidewalls <b>29</b>, <b>31</b> of the body extension <b>28</b>. The bracket body <b>12</b> and latching member <b>14</b> are arranged such that tubular region <b>60</b> is juxtaposed with cylindrical opening <b>56</b> and tubular region <b>62</b> is juxtaposed with cylindrical opening <b>58</b>. In the representative embodiment, tubular regions <b>60</b>, <b>62</b> each have an oval cross-sectional profile from a perspective viewed parallel to the axis of rotation <b>41</b> of the hinge pin <b>16</b>. More specifically, the tubular regions <b>60</b>, <b>62</b> in the representative embodiment are oval or slotted in shape with each consisting of two concave end surfaces connected by parallel planar surfaces and a major axis of the slot aligned substantially parallel to the non-collinear direction <b>90</b>. When the bracket base <b>18</b> is secured to the tooth, the major axis of each of the tubular regions <b>60</b>, <b>62</b> is oriented substantially in the gingival-occlusal direction and may be orthogonal to the axis of rotation <b>41</b>.

A tubular chamber or region <b>64</b> of the passageway <b>42</b> is disposed centrally between the two tubular regions <b>60</b>, <b>62</b>. The tubular region <b>64</b> has a substantially cylindrical shape with a circular cross-sectional profile when viewed from a perspective parallel to the axis of rotation <b>41</b> of the hinge pin <b>16</b>. A corresponding central region <b>15</b> of the hinge pin <b>16</b> is engaged with the tubular region <b>64</b> of passageway <b>42</b> to mechanically couple the latching member <b>14</b> with the bracket body <b>12</b>. Tubular region <b>64</b> has a short axial length in comparison with the axial length of the tubular regions <b>60</b>, <b>62</b> so that the hinge pin <b>16</b> is secured within the passageway <b>42</b> over a relatively short portion of its entire length. The central region <b>15</b> of the hinge pin <b>16</b> and the tubular region <b>64</b> of passageway <b>42</b> have a close tolerance fit that may be established by a staking process using a pointed tool that creates a tapered perforation <b>59</b> in the bracket body and causes the material of the bracket body <b>12</b> surrounding tubular region <b>64</b> to deform. The resulting deformation region <b>57</b> supplies the mechanical engagement between the bracket body <b>12</b> and the central region <b>15</b> of hinge pin <b>16</b> and constrains movement of the central region <b>15</b> of hinge pin <b>16</b> relative to the bracket body <b>12</b>.

A first intermediate region <b>17</b> of the hinge pin <b>16</b>, which is disposed along the axial length of the hinge pin <b>16</b> between the projecting end <b>52</b> and the secured central region <b>15</b>, is positioned in tubular region <b>60</b>. A second intermediate region <b>19</b> of the hinge pin <b>16</b>, which is disposed along the axial length of the hinge pin <b>16</b> between the projecting end <b>54</b> and the secured central region <b>15</b>, is positioned in the other tubular region <b>62</b>. The tubular regions <b>60</b>, <b>62</b>, which have a larger cross sectional area when viewed along the axis of rotation <b>41</b> than the central tubular region <b>64</b>, provide clearance or relief spaces for the flexing of the intermediate portions <b>17</b>, <b>19</b> of the hinge pin <b>16</b>.

The tubular regions <b>60</b>, <b>62</b> may be shaped to allow bidirectional flexing of the hinge pin <b>16</b> in substantially one plane bounded between the opposite concave end surfaces of tubular regions <b>60</b>, <b>62</b> and constrained by the planar surfaces of regions <b>60</b>, <b>62</b> between the concave end surfaces, or may be alternatively shaped to permit flexing in a multitude of directions. This permits the intermediate regions <b>17</b>, <b>19</b> of the hinge pin <b>16</b> and the latching member <b>14</b> to move in a direction generally indicated by single headed arrow <b>90</b> that is not collinear with the axis of rotation <b>41</b>. In one embodiment, the non-collinear direction <b>90</b> is oriented to be perpendicular to the axis of rotation <b>41</b>.

This alternative bidirectional design gives the hinge pin <b>16</b> the room needed for flexing when the latching member <b>14</b> is near the closed position, but restricts movement when the latching member is in other positions, such as the opened position or any position between the opened and closed positions. Limiting the movement of the hinge pin <b>16</b>, for example, in the labial/lingual direction may enhance control over the archwire <b>33</b> because the latching member <b>14</b> is constrained by the hinge pin <b>16</b> in the labial/lingual direction.

Arm <b>48</b> of the latching member <b>14</b> includes an optional detent <b>66</b> defined as an outwardly-projecting ridge that bulges outwardly and interrupts an otherwise smoothly curved surface. Similarly, arm <b>50</b> of the latching member <b>14</b> includes an optional detent <b>68</b> also defined as an outwardly-projecting ridge that interrupts an otherwise smoothly curved surface. The detents <b>66</b>, <b>68</b>, which are aligned generally parallel to the axis of rotation <b>41</b>, cooperate to hold the latching member <b>14</b> in the opened position (<figref idref="DRAWINGS">FIGS. 5</figref>, <b>6</b>) by engaging a portion of a corresponding one of the lands <b>44</b>, <b>46</b>. The resistance provided by this engagement is selected to be adequate to prevent inadvertent closing by a force applied to the latching member <b>14</b>, when the latching member <b>14</b> is in the opened position, that is below a certain threshold magnitude. The resistance provided by the detents <b>66</b>, <b>68</b> is selected to be easily overcome by application of a pivoting force about the axis of rotation <b>41</b> that is greater than the threshold magnitude for movement and directed to pivot the latching member <b>14</b> from the opened position toward the closed position.

The archwire slot <b>32</b> has an entrance opening defined between side surfaces <b>34</b>, <b>36</b>. Body extension <b>30</b> has a labial surface <b>30</b><i>a </i>covering a labial side of the bracket body <b>12</b> and the body extension <b>28</b> has a labial surface <b>28</b><i>a </i>covering another labial side of the bracket body <b>12</b> that is separated from labial surface <b>30</b><i>a </i>by the access opening of the archwire slot <b>32</b>. For purposes of description, the labial sides of the bracket body <b>12</b> may be considered to be divided at a boundary extending through a center plane of the archwire slot <b>32</b>.

With continued reference to <figref idref="DRAWINGS">FIGS. 1-5</figref>, the main body <b>40</b> of latching member <b>14</b> has a rear surface <b>69</b> that closes the access opening into the archwire slot <b>32</b> and confronts the archwire <b>33</b> when the latching member <b>14</b> is in the closed position. The main body <b>40</b> also includes a front surface <b>67</b> that faces away from the archwire slot <b>32</b> and bonding base <b>18</b>, when the latching member <b>14</b> is in the closed position, and toward the cheek or lips, when the bracket <b>10</b> is mounted to a tooth. The main body <b>40</b> of the latching member <b>14</b> includes a side edge <b>71</b> that is opposite to side edge <b>49</b> of the main body <b>40</b> from which the arms <b>48</b>, <b>50</b> project and opposite side edges <b>61</b>, <b>63</b> that connect side edges <b>49</b>, <b>71</b>. The arms <b>48</b>, <b>50</b> curve slightly inwardly relative to the rear surface <b>69</b> of the main body <b>40</b> toward the lands <b>44</b>, <b>46</b>. The arms <b>48</b>, <b>50</b> and the lands <b>44</b>, <b>46</b> have complementary curvatures.

The orthodontic bracket <b>10</b> includes a latch mechanism that relies on cooperation between the hinge pin <b>16</b> and structures formed on the bracket body <b>12</b> and the main body <b>40</b> of the latching member <b>14</b>, as described below, to secure the closed latching member <b>14</b> with the bracket body <b>12</b>. Extending laterally along width, w, of the main body <b>40</b> at a location between the side edge <b>71</b> and the front surface <b>67</b> is a locking lip <b>72</b>. The locking lip <b>72</b> includes a locking surface <b>79</b> and a contoured surface <b>70</b> that joins the surface <b>79</b> of locking lip <b>72</b> with the front surface <b>67</b>. Surface <b>79</b> of locking lip <b>72</b> and contoured surface <b>70</b> bound two sides of a groove that also extends laterally along the width, w, of the main body <b>40</b>. When the latching member <b>14</b> is mounted to the bracket body <b>12</b> and pivoted to the closed position, the locking lip <b>72</b> and side edge <b>71</b> are located proximate to the body extension <b>30</b> with the side edge <b>71</b> having a confronting relationship with the body extension <b>30</b>.

A chamfered surface <b>74</b> is defined on the main body <b>40</b> between the rear surface <b>69</b> and the side edge <b>71</b>. The chamfered surface <b>74</b>, which is inclined at a shallow angle relative to the rear surface <b>69</b>, is beneficial for use in latching the latching member <b>14</b> in the closed position, as described in greater detail below and as best shown in <figref idref="DRAWINGS">FIGS. 3 and 3A</figref>. The side edge <b>71</b>, locking lip <b>72</b>, and chamfered surface <b>74</b> extend along the main body <b>40</b> with a fixed spatial relationship and are generally aligned with the axis of rotation <b>41</b>. The side edge <b>71</b>, locking surface <b>79</b> of locking lip <b>72</b>, and chamfered surface <b>74</b> also connect the rear and front surfaces <b>67</b>, <b>69</b> of the main body <b>40</b>. In the illustrated embodiment, the main body <b>40</b> has a substantially uniform thickness so that the separation between the rear and front surfaces <b>67</b>, <b>69</b> is independent of location on the main body <b>40</b> and so that the rear and front surfaces <b>67</b>, <b>69</b> are contained in substantially parallel planes.

The body extension <b>30</b> includes an undercut region or recess <b>78</b> defined between an inclined surface <b>77</b> of a ledge or lip <b>76</b> and a shoulder <b>80</b> formed in the bracket body <b>12</b>. A surface <b>75</b> joins surface <b>77</b> with shoulder <b>80</b>. The inclined surface <b>77</b> of lip <b>76</b> confronts the surface <b>79</b> of lip <b>76</b>, which is also inclined. The surfaces <b>77</b>, <b>79</b> are inclined at approximately equal inclination angles. The recess <b>78</b> is located on opposite side of the bracket body <b>12</b> from the passageway <b>42</b>. The recess <b>78</b> opens generally in the non-collinear direction <b>90</b>.

The shoulder <b>80</b> adjoins side surface <b>36</b> of the archwire slot <b>32</b> along a tight radius corner. A contoured surface <b>85</b> is defined where the labial surface <b>30</b><i>a </i>of the body extension <b>30</b> intersects the entrance to archwire slot <b>32</b>. The lip <b>76</b> and shoulder <b>80</b> are separated by a distance that permits the locking lip <b>72</b> to be placed in the recess <b>78</b> when the latching member <b>14</b> is closed and latched. In the closed position with the lips <b>72</b>, <b>76</b> engaged, forces transferred from the archwire <b>33</b> to the bracket body <b>12</b> will not disengage the latching member <b>14</b> from its locked condition.

When the latching member <b>14</b> is closed, the hinge pin <b>16</b> locates the latching member <b>14</b> relative to the bracket body <b>12</b> such that the end of the latching member <b>14</b> carrying the lip <b>72</b> toward the locked position so that the lips <b>72</b>, <b>76</b> are confronting and mutually engaged. The recess <b>78</b> has a depth measured between surface <b>75</b> and the location where surface <b>77</b> meets contoured surface <b>85</b>. The depth of the recess <b>78</b> and the flexibility of the material forming the hinge pin <b>16</b> are selected such that the latching member <b>14</b> can be moved a distance in the non-collinear direction <b>90</b> adequate to engage the lip <b>72</b> with the recess <b>78</b> to place the latching member <b>14</b> in the closed position and to disengage the lip <b>72</b> from the recess <b>78</b> to release the latching member <b>14</b> from the closed position. The lips <b>72</b>, <b>76</b> have an interlocking relationship in the closed position, although the invention is not so limited. For example, lip <b>76</b> in the body extension <b>30</b> may be modified so that the lips <b>72</b>, <b>76</b> (and lip <b>72</b> and recess <b>78</b>) do not exhibit an interlocking relationship when the latching member <b>14</b> is closed, as depicted in an alternative embodiment shown in <figref idref="DRAWINGS">FIG. 12</figref>.

The inclined surfaces <b>77</b>, <b>79</b> contact each other when the latching member <b>14</b> is in the closed position such that the lip <b>76</b> of the latching member <b>14</b> is interlocked with the recess <b>78</b> of the bracket body <b>12</b>. In the representative embodiment, surface <b>79</b> on lip <b>72</b> and surface <b>77</b> on lip <b>76</b> are substantially flat or planar with complementary inclination angles so that the lips <b>72</b>, <b>76</b> interlock to provide additional resistance against movement of the latching member <b>14</b> relative to the bracket body <b>12</b>. However, the invention is not so limited. When the latching member <b>14</b> is moved in the non-collinear direction <b>90</b>, the hinge pin <b>16</b> applies a spring bias that resists the movement.

The lips <b>72</b>, <b>76</b> have an interlocking relationship, although the invention is not so limited. For example, lip <b>76</b> in the body extension <b>30</b> may be modified so that the lips <b>72</b>, <b>76</b> do not exhibit an interlocking relationship when the latching member <b>14</b> is closed, as depicted in an alternative embodiment shown in <figref idref="DRAWINGS">FIG. 12</figref> and as described below.

In an alternative embodiment and as shown in <figref idref="DRAWINGS">FIG. 3B</figref>, the latch mechanism of bracket body <b>12</b> and latching member <b>14</b> may be modified to change the configuration of the latch mechanism. Specifically, the lip of latching member <b>14</b> includes a surface <b>72</b><i>a </i>that is connected by contoured surface <b>70</b> with the front surface <b>67</b>. The body extension <b>30</b> includes a ledge or lip <b>76</b><i>a</i>, which is similar to locking lip <b>76</b>, having a surface <b>77</b><i>a </i>that overhangs the recess <b>78</b>. In this alternative embodiment, surfaces <b>72</b><i>a</i>, <b>77</b><i>a </i>are not inclined relative to each other so that the latch mechanism is not interlocking.

With renewed reference to <figref idref="DRAWINGS">FIGS. 1-5</figref>, the orthodontic bracket <b>10</b> includes a round tool hole or opening, generally indicated by reference numeral <b>82</b>, that is exposed from the labial/buccal direction when the bracket base <b>18</b> is bonded with the patient's tooth surface. The tool opening <b>82</b> is defined partially by a concave region <b>84</b> defined along the side edge <b>71</b> of latching member <b>14</b> and partially by a concave region <b>86</b> defined on a side edge of the body extension <b>30</b> that faces the archwire slot <b>32</b>. When the latching member <b>14</b> is in the closed position, the concave regions <b>84</b>, <b>86</b> are confronting and registered relative to each other to define the tool opening <b>82</b>. Concave region <b>86</b> includes a curved sidewall <b>87</b> that extends into the bracket body <b>12</b> and concave region <b>84</b> has a curved sidewall <b>83</b> that penetrates through the latching member <b>14</b>. The curved sidewalls <b>83</b>, <b>87</b> are arranged about a central axis that is inclined relative to the plane of the bonding base <b>18</b>.

In the representative embodiment, the locking lips <b>72</b>, <b>76</b> are depicted as complementary flat surfaces, although the invention is not so limited. In the representative embodiment of the latching member <b>14</b>, the continuity of the contoured surface <b>70</b>, side edge <b>71</b>, and locking lip <b>72</b> is interrupted by the concave region <b>84</b>. However, the lateral extent or length of the contoured surface <b>70</b>, side edge <b>71</b>, and locking lip <b>72</b> along the width, w, of the main body <b>40</b> and between side edges <b>61</b>, <b>63</b> is a design parameter determined according to, for example, the application for the bracket <b>10</b>. The contoured surface <b>70</b>, side edge <b>71</b>, and locking lip <b>72</b> may be shorter than shown in the representative embodiment, may begin at a location along the width, w, of the main body <b>40</b> other than proximate to the side edges <b>61</b>, <b>63</b>, may end at a location along the width, w, of the main body <b>40</b> other than proximate to the concave region <b>84</b>, and may have asymmetrical lengths and locations.

As shown in <figref idref="DRAWINGS">FIG. 1</figref>, the latching member <b>14</b> may be opened using an instrument <b>91</b> with a tip <b>92</b> dimensioned to be inserted into the circular tool opening <b>82</b>. The instrument <b>91</b> is manually held by the clinician using a grip portion (not shown). The tool opening <b>82</b> may be slightly angled as shown in the representative embodiment or, in an alternative embodiment, may be vertically oriented. Angling the tool opening <b>82</b> may place the instrument <b>91</b> at a more comfortable angle for use by the clinician.

In an alternative embodiment of the invention, a small dimensional clearance may be provided between the rear surface <b>69</b> of the latching member <b>14</b> and the shoulder <b>80</b> formed in the bracket body <b>12</b>. When the latching member <b>14</b> is in the closed position, the dimensional clearance may be advantageous for changing the distance between the rear surface <b>69</b> of the latching member <b>14</b> and the base surface <b>38</b> of the archwire slot <b>32</b>. This effectively decreases the height of the archwire slot <b>32</b> by changing the clearance between the rear surface <b>69</b> and the archwire <b>33</b>. The change is implemented by mounting a ligature in the form of an elastomeric O-ring to the bracket <b>10</b> about one of the body extensions <b>28</b>, <b>30</b> in a manner that applies a force to the latching member <b>14</b> directed toward the base surface <b>38</b> of the archwire slot <b>32</b>. This feature may be beneficial when a clinician is finishing an orthodontic treatment and provides the clinician with an additional degree of flexibility.

An identification marking <b>98</b> (<figref idref="DRAWINGS">FIGS. 2 and 8</figref>), which is preferably one or more alphanumeric characters and/or symbols, may be defined in the base slot surface <b>38</b> bounding the archwire slot <b>32</b>. The optional identification marking <b>98</b> may be used as a visible indicator to the clinician that denotes bracket location and permits the clinician to distinguish between high and low torque brackets <b>10</b>. In the latter regard, one such system includes inscribing an “H” as one of the alphanumeric characters to identify a high torque bracket <b>10</b> or an “L” as one of the alphanumeric characters to identify a low torque bracket <b>10</b>. Conventional techniques for forming the identification marking <b>98</b>, which are known to persons having ordinary skill in the art, may apply the identification marking <b>98</b> either during the fabrication of the bracket body <b>12</b> or after the bracket body <b>12</b> is fabricated.

In use and with reference to <figref idref="DRAWINGS">FIGS. 1-8</figref>, the orthodontic bracket <b>10</b> is typically applied to the patient's teeth as part of a set of similar brackets <b>10</b>. The bracket base <b>18</b> on the bracket body <b>12</b> is mounted to the buccolabial surface of a tooth (not shown). At the time of mounting, the latching member <b>14</b> is initially in the opened condition, as shown in <figref idref="DRAWINGS">FIGS. 5 and 6</figref>. The archwire <b>33</b> is installed in the archwire slot <b>32</b>. The latching member <b>14</b> is pivoted about the axis of rotation <b>41</b> along hinge pin <b>16</b> toward the body extension <b>28</b>, as indicated by single headed arrow <b>88</b> (<figref idref="DRAWINGS">FIG. 6</figref>).

As the latching member <b>14</b> is pivoted, the chamfered surface <b>74</b> on the latching member <b>14</b> eventually physically contacts contoured surface <b>85</b> on the body extension <b>30</b>. As shown in <figref idref="DRAWINGS">FIGS. 7 and 8</figref>, a force is applied to the latching member <b>14</b> in a direction generally indicated by single headed arrow <b>88</b> that is sufficient to place the latching member <b>14</b> in the closed position. Cooperation between the applied force <b>88</b> and the physical contact creates a camming action that moves the latching member <b>14</b> in the non-collinear direction <b>90</b> against an increasing spring bias applied by the hinge pin <b>16</b>. This camming action provides a mechanical advantage that permits the latching member <b>14</b> to be closed and latched, if the clinician desires, without the assistance of a special tool or instrument.

The central region <b>15</b> of the hinge pin <b>16</b> has a fixed relationship with the central region <b>64</b> of the passageway <b>42</b>. Under the influence of the applied force <b>88</b>, the intermediate regions <b>17</b>, <b>19</b> of the hinge pin <b>16</b> flex or move in the non-collinear direction <b>90</b> within the relief spaces defined by the tubular regions <b>60</b>, <b>62</b>, as evident from a comparison of <figref idref="DRAWINGS">FIGS. 2 and 8</figref>. Specifically, the tubular regions <b>60</b>, <b>62</b> provide clearance for resilient deflection of the intermediate regions <b>17</b>, <b>19</b> of the hinge pin <b>16</b> to flex in the non-collinear direction <b>90</b>. The material forming the hinge pin <b>16</b> has sufficient flexibility to permit flexing in the non-collinear direction <b>90</b> to an extent sufficient to permit the locking lip <b>72</b> on the latching member <b>14</b> to clear the lip <b>76</b> on the body extension <b>30</b>. Direction <b>90</b> is non-collinear relative to the axis of rotation <b>41</b>. The central region <b>15</b> of the hinge pin <b>16</b> is secured in the tubular region <b>64</b> against movement in the non-collinear direction <b>90</b> so that the intermediate regions <b>17</b>, <b>19</b> of the hinge pin <b>16</b> can move in the respective tubular regions <b>60</b>, <b>62</b>.

When locking lip <b>72</b> clears lip <b>76</b>, the spring bias applied to the latching member <b>14</b> by the hinge pin <b>16</b> forces the latching member <b>14</b> to move in the occlusal-gingival direction (i.e., in a direction opposite to the non-collinear direction <b>90</b>). The directional spring bias urges the end of the latching member <b>14</b> carrying the locking lip <b>72</b> toward the locked and closed position so that the lips <b>72</b>, <b>76</b> are confronting and mutually engaged. When the hinge pin <b>16</b> is subsequently moved by an applied force in the non-collinear direction <b>90</b> to open or close the latching member <b>14</b>, the spring bias applied to the latching member <b>14</b> increases and opposes the movement in direction <b>90</b>. In particular, the increase in the spring bias applied to the latching member <b>14</b> by the hinge pin <b>16</b> resists inadvertent opening of the closed latching member <b>14</b> and exerts a constant force that acts to maintain the latching member <b>14</b> in the closed position with the lip <b>72</b> secured in the recess <b>78</b>.

In the closed position (<figref idref="DRAWINGS">FIG. 3</figref>), a significant portion of the main body <b>40</b> of the latching member <b>14</b> overlies the side surfaces <b>34</b>, <b>36</b> and base surface <b>38</b> of the archwire slot <b>32</b>. The archwire <b>33</b> positioned in the archwire slot <b>32</b> is blocked against removal by movement in a direction normal to the base surface <b>38</b> by the rear surface <b>69</b> of the latching member <b>14</b>. The archwire <b>33</b> is trapped against movement in the occlusal-gingival direction by the side surfaces <b>34</b>, <b>36</b>. In this self-ligating manner, closing the latching member <b>14</b> ligates the archwire <b>33</b> to the bracket <b>10</b>. No additional loose ligatures are required to retain the archwire <b>33</b> in the archwire slot <b>32</b>.

A procedure for opening the latching member <b>14</b> from its closed position to remove the archwire <b>33</b> from the archwire slot <b>32</b> may be described with specific references to <figref idref="DRAWINGS">FIGS. 9A-C</figref>. As best shown in <figref idref="DRAWINGS">FIG. 9A</figref>, the clinician maneuvers the instrument <b>91</b> to insert the tip <b>92</b> in the circular opening <b>82</b>. As best shown in <figref idref="DRAWINGS">FIG. 9B</figref>, the instrument <b>91</b> uses the body extension <b>30</b> of bracket body <b>12</b> as a fulcrum point for moving the latching member <b>14</b> in a direction <b>96</b> generally opposed to the spring bias applied by the hinge pin <b>16</b> and generally collinear with the non-collinear direction <b>90</b>. This causes the intermediate regions <b>17</b>, <b>19</b> of the hinge pin <b>16</b> to freely flex in the oval regions <b>60</b>, <b>62</b> of the passageway <b>42</b>.

When the lip <b>72</b> carried on the latching member <b>14</b> clears the edge of lip <b>76</b> on the body extension <b>30</b> of bracket body <b>12</b>, the instrument <b>91</b> is manipulated to pivot the front side edge <b>71</b> of the latching member <b>14</b> upward so that, when the tip <b>92</b> is removed, the action of the spring bias does not reengage the lips <b>72</b>, <b>76</b>. The latching member <b>14</b> is released to be pivoted about the axis of rotation <b>41</b> toward the opened position. In the opened position, the optional detents <b>66</b>, <b>68</b> may secure the latching member <b>14</b> against inadvertently closing.

With reference to <figref idref="DRAWINGS">FIGS. 10</figref>, <b>10</b>A, and <b>11</b> in which like reference numerals refer to like features in <figref idref="DRAWINGS">FIGS. 1-9</figref> and in accordance with an alternative embodiment, an orthodontic bracket <b>10</b><i>a </i>may include a hinge pin <b>102</b> having a non-circular profile in cross section when viewed along an axis of rotation <b>41</b>. In one specific embodiment, the hinge pin <b>102</b> may have a non-cylindrical, cross-sectional profile, when viewed along the axis of rotation <b>41</b>, that is rectangular. The hinge pin <b>102</b> includes a rectangular central region <b>104</b> analogous to central region <b>15</b> (<figref idref="DRAWINGS">FIGS. 1-9</figref>) of hinge pin <b>16</b>, rectangular opposite ends <b>106</b>, <b>108</b> analogous to the opposite ends <b>52</b>, <b>54</b> of the hinge pin <b>16</b> (<figref idref="DRAWINGS">FIGS. 1-9</figref>), and rectangular intermediate regions <b>110</b>, <b>112</b> analogous to the intermediate regions <b>17</b>, <b>19</b> of hinge pin <b>16</b> (<figref idref="DRAWINGS">FIGS. 1-9</figref>). Intermediate region <b>110</b> is disposed along the axis of rotation <b>41</b> between central region <b>104</b> and end <b>106</b>. Intermediate region <b>112</b> is disposed along the axis of rotation <b>41</b> between central region <b>104</b> and end <b>108</b>.

Arm <b>48</b> of the latching member <b>14</b> has an opening <b>114</b> and arm <b>50</b> of the latching member has an opening <b>116</b>. The openings <b>114</b>, <b>116</b>, which are analogous to cylindrical openings <b>56</b>, <b>58</b> (<figref idref="DRAWINGS">FIGS. 1-9</figref>), are non-cylindrical and, in the representative embodiment, are D-shaped to provide clearance for the pivoting of the hinge pin <b>102</b> when the latching member <b>14</b> is moved between the opened and closed positions. The D-shape of each of the openings <b>114</b>, <b>116</b> is defined by a curved portion <b>120</b>, a linear portion <b>122</b>, and intervening line segment portions <b>123</b>, <b>124</b> connecting each opposite end of the curved portion <b>120</b> with respective opposite ends of the linear portion <b>122</b>. The curved portion <b>120</b> may be semicircular, as shown in <figref idref="DRAWINGS">FIG. 10</figref>.

The body extension <b>28</b> of the bracket body <b>12</b> has a passageway <b>130</b> that is analogous to passageway <b>42</b> (<figref idref="DRAWINGS">FIGS. 1-9</figref>). Passageway <b>130</b> includes a tubular region <b>132</b> analogous to the tubular region <b>64</b> (<figref idref="DRAWINGS">FIGS. 1-9</figref>) of passageway <b>42</b> and tubular regions <b>134</b>, <b>136</b> that flank the centrally-located tubular region <b>132</b>. Tubular regions <b>134</b>, <b>136</b> are analogous to tubular regions <b>60</b>, <b>62</b> (<figref idref="DRAWINGS">FIGS. 1-9</figref>) of passageway <b>42</b>. The tubular regions <b>132</b>, <b>134</b>, <b>136</b> of passageway <b>130</b>, which are arranged along the axis of rotation <b>41</b>, have a rectangular cross-section, when viewed along the axis of rotation <b>41</b>. Tubular region <b>132</b> penetrates through sidewall <b>29</b> of the body extension <b>28</b> and tubular region <b>134</b> penetrates through sidewall <b>31</b> of the body extension <b>28</b>.

The cross-sectional area of tubular region <b>132</b> of passageway <b>130</b> is approximately equal to the cross-sectional area of the central region <b>104</b> of hinge pin <b>102</b>, which fixes the location of the central region <b>104</b> relative to the bracket body <b>12</b>. Tubular region <b>134</b> of passageway <b>130</b> narrows in cross-sectional area from its intersection at an open end with sidewalls <b>29</b> to its merger with one of the opposite open ends of the centrally-located tubular region <b>132</b>. Similarly, tubular region <b>136</b> of passageway <b>130</b> narrows in cross-sectional area from its intersection at an open end with sidewall <b>31</b> to its merger with the other of the opposite open ends of tubular region <b>132</b>.

Tubular region <b>134</b> of passageway <b>130</b> is bounded by side surfaces <b>142</b>, <b>144</b>, <b>146</b>, <b>148</b> in which adjacent pairs of the side surfaces <b>142</b>, <b>144</b>, <b>146</b>, <b>148</b> converge at corners. In the representative embodiment, side surface <b>142</b> is inclined relative to the other bounding side surfaces <b>144</b>, <b>146</b>, <b>148</b> to provide the narrowing in cross-sectional area of region <b>142</b>. Tubular region <b>136</b> is bounded by a similar set of side surfaces such that the description of tubular region <b>134</b> is understood to apply equally to apply to tubular region <b>134</b>. The enlarged cross-sectional area of tubular regions <b>134</b>, <b>136</b>, in comparison with the cross-sectional area of the intermediate regions <b>110</b>, <b>112</b> of hinge pin <b>102</b> at the same location along the axis of rotation <b>41</b>, provides the relief spaces for the flexing of the intermediate regions <b>110</b>, <b>112</b> of hinge pin <b>102</b>, as described above with regard to tubular regions <b>60</b>, <b>62</b> of passageway <b>42</b> (<figref idref="DRAWINGS">FIGS. 1-9</figref>). Side surfaces <b>142</b>, <b>146</b> are aligned generally in a plane parallel to the plane of side surfaces <b>34</b>, <b>36</b> of archwire slot <b>32</b>.

When the latching member <b>14</b> is closed, the intermediate regions <b>110</b>, <b>112</b> of hinge pin <b>102</b> are substantially aligned with the linear portion <b>122</b> of each of the openings <b>114</b>, <b>116</b> and with the side surfaces <b>142</b>, <b>146</b>. This relative arrangement and orientation between the intermediate regions <b>110</b>, <b>112</b> and the passageway <b>130</b> makes the latching member <b>14</b> fairly secure in the lingual-gingival direction because the side surfaces <b>144</b>, <b>148</b> of each of the tubular regions <b>134</b>, <b>136</b> limit motion of the intermediate regions <b>110</b>, <b>112</b> in a direction parallel with side surfaces <b>144</b>, <b>148</b>. This blocked motion generally prevents the latching member <b>14</b> from moving labially under the influence of forces applied by the archwire <b>33</b>. The spring bias applied to the latching member <b>14</b> by the hinge pin <b>102</b> resiliently biases the lip <b>72</b> into recess <b>78</b> in a direction opposite to the non-collinear direction <b>90</b> (<figref idref="DRAWINGS">FIGS. 7</figref>, <b>8</b>). The minor dimension of the intermediate regions <b>110</b>, <b>112</b> of hinge pin <b>102</b> is shorter than the distance between the side surfaces <b>142</b>, <b>146</b> in each of tubular regions <b>134</b>, <b>136</b>, which allows room for the intermediate regions <b>110</b>, <b>112</b> to flex when the latching member <b>14</b> is moved to open and close the bracket <b>10</b><i>a. </i>

With reference to <figref idref="DRAWINGS">FIGS. 12 and 13</figref> in which like reference numerals refer to like features in <figref idref="DRAWINGS">FIGS. 1-9</figref> and in accordance with an alternative embodiment, an orthodontic bracket <b>160</b>, which is otherwise identical to bracket <b>10</b>, includes bracket body <b>162</b> and a latching member <b>164</b> that have been modified to situate the relief spaces (i.e., oval and circular cross section regions) for the hinge pin <b>16</b> in the latching member <b>164</b>. To that end, a body extension <b>166</b> of the bracket body <b>162</b> includes a spaced-apart pair of supports <b>168</b>, <b>170</b> positioned near the sidewalls <b>20</b>, <b>22</b>, respectively. Support <b>168</b> includes an opening <b>172</b> that is engaged with the projecting end <b>52</b> of the hinge pin <b>16</b>. Support <b>170</b> includes an opening <b>174</b> that is engaged with projecting end <b>54</b> of the hinge pin <b>16</b>. The multiple laterally-spaced pivot points defined by the engagement between the projecting ends <b>52</b>, <b>54</b> of the hinge pin <b>16</b> and the openings <b>170</b>, <b>172</b>, respectively, for opening and closing the bracket <b>160</b>, therefore, differ from the single central pivot point of bracket <b>10</b> (<figref idref="DRAWINGS">FIGS. 1-9</figref>). However, the operation and structure of the bracket <b>160</b> is substantially the same as for bracket <b>10</b>, as is the method of using the bracket <b>160</b>.

To that end, the latching member <b>164</b> includes a passageway <b>188</b> that is analogous in construction to passageway <b>42</b> in bracket body <b>12</b> (<figref idref="DRAWINGS">FIGS. 1-9</figref>). Along the majority of its length, the passageway <b>188</b> has tubular regions <b>190</b>, <b>192</b> of relatively large cross-sectional area. The tubular regions <b>190</b>, <b>192</b>, which are similar in construction and function to tubular regions <b>60</b>, <b>62</b> (<figref idref="DRAWINGS">FIGS. 1-9</figref>), are oriented with a major axis of the oval-shaped cross-sectional profile substantially aligned in the gingival-occlusal direction when the bracket base <b>18</b> is secured to the tooth. The intermediate regions <b>17</b>, <b>19</b> of the hinge pin <b>16</b> reside in the tubular regions <b>190</b>, <b>192</b>. A tubular region <b>194</b> of the passageway <b>188</b>, which is centrally disposed between tubular regions <b>190</b>, <b>192</b>, has a shape complementary to the shape of the hinge pin <b>16</b> and is connected with the central region <b>15</b> of hinge pin <b>16</b>. As a result, the intermediate regions <b>17</b>, <b>19</b> of the hinge pin <b>16</b> can resiliently deflect within the tubular regions <b>190</b>, <b>192</b> of passageway <b>188</b> in the non-collinear direction <b>90</b> (<figref idref="DRAWINGS">FIGS. 7</figref>, <b>8</b>) relative to the central region <b>15</b> of the hinge pin <b>16</b>, which is secured against movement in the non-collinear direction <b>90</b> (<figref idref="DRAWINGS">FIGS. 7</figref>, <b>8</b>).

While the invention has been illustrated by a description of various preferred embodiments and while these embodiments have been described in considerable detail in order to describe the best mode of practicing the invention, it is not the intention of applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications within the spirit and scope of the invention will readily appear to those skilled in the art. The invention itself should only be defined by the appended claims, wherein